Bonding system for dual walled turbine components

ABSTRACT

A system is for bonding a cover sheet to a core to form or repair a dual wall structure. The system includes a cover sheet probe and an inner pedestal probe. A three dimensional contoured tip of the cover sheet probe abuts against a three dimensional contoured outer surface of the cover sheet opposite a pedestal of the core. The pedestal abuts the inner surface of the cover sheet. The inner pedestal probe may be coupled to the core to create a conductive electrical path from the cover sheet probe through at least part of the structure. A flow of electric power is controlled and supplied to the cover sheet probe to heat a junction between the area of the cover sheet abutting the pedestal and the pedestal. A heated area is created in the junction and fixedly couples the coversheet and the pedestal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of, and claims priorityunder 35 USC § 120 to U.S. nonprovisional application 16/807,107, filedMar. 2, 2020, the entire contents of which are incorporated byreference.

TECHNICAL FIELD

This disclosure relates to dual wall structures that have manyapplications. Specific applications disclosed relate to combustionturbines and, in particular, to complex geometry dual wall turbinecomponent bonding.

BACKGROUND

Gas turbine engines generate large amounts of internal heat due tocombustion processes. As a result, engine components, such as turbineblades, may experience high thermal loads. The use of dual walledstructures in turbine engine components allows for higher operatingtemperatures.

Likewise, aircraft engines and aircraft themselves require low density,high strength structures, which are often created by using dual wallpanels. The disclosed system and method can be used to create a widevariety of dual walled structures using many different materials. Thesedual walled structures have value for turbine engine components,aircraft components, and other industrial structures such as heatexchangers, cooled structures, low density rigid structures, reactionmanifolding, and reaction plenums/chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments may be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale. Moreover, in the figures, like-referenced numeralsdesignate corresponding parts throughout the different views.

FIG. 1 is a cross-sectional view of an example of a gas turbine engine;

FIG. 2 illustrates an example of a portion of a three dimensionalcontoured dual wall structure;

FIG. 3 illustrates an example of a bonding system;

FIG. 4 illustrates an example of a probe;

FIG. 5 illustrates another example of a probe;

FIG. 6 illustrates a second example of the bonding system and a cut-awayview of a 3D contoured dual wall structure;

FIG. 7 illustrates a third example of the bonding system and 3Dcontoured dual wall structure;

FIG. 8 illustrates a fourth example of the bonding system and a cut-awayview of a 3D contoured dual wall structure;

FIG. 9 illustrates a fifth example of the bonding system and a cut-awayview of a 3D contoured dual wall structure;

FIG. 10 illustrates a sixth example of the bonding system and a cut-awayview of a 3D contoured dual wall structure.

DETAILED DESCRIPTION

Described herein is a system for bonding dual wall structures such asturbine engine components, for example, blades, vanes, endwalls, and/orother similar components. A blade is disclosed to demonstrate theability to create complex dual wall geometries. The system includes aresistance welder, a cover sheet probe, an inner pedestal probe, and anairfoil. The resistance welder is used for bonding, for exampleresistance bonding, diffusion bonding, and/or brazing/braze bonding. Thedual walled turbine component includes a core and a cover sheet. Thecore may include a pedestal and/or a series of pedestals and otherfeatures. The cover sheet probe, the pedestal and inner and outersurfaces of the cover sheet may have highly contoured surfaces thatalign with each other. The highly contoured surfaces are threedimensional.

The highly contoured inner surface of the cover sheet abuts and followsthe highly contoured surface of the pedestal. The cover sheet probe andthe inner pedestal probe are electrically coupled to the resistancewelder. The cover sheet probe may include a tip with a contacting area.The contacting area may have a three dimensional (3D) contoured surfacethat may match or follow the 3D contour of the outer surface of thecover sheet. The contacting area may abut against the outer surface ofthe cover sheet opposite the inner surface of the cover sheet abuttingthe pedestal. The contacting area may be equal to or greater than asurface area of the pedestal. A pressing force may be applied to theouter surface of the cover sheet by the tip of the cover sheet probe.The inner pedestal probe may be electrically coupled to the airfoil. Aconductive electric path may be formed from the cover sheet probe to theinner pedestal probe through the airfoil. The conductive path mayinclude at least part of the pedestal. The resistance welder may supplyelectric power to the cover sheet probe and form a heated area at thejunction of the cover sheet and the pedestal.

An aspect of the system includes aligning a pedestal, and/or series ofpedestals and other features, of the core of a dual wall structure, suchas a turbine blade, with a cover sheet of the dual wall structure sothat the cover sheet and pedestal are in contact with each other. Acover sheet probe is placed in contact with the cover sheet. A tip ofthe cover sheet probe may have a three dimensional contoured surface tofollow and align with a three dimensional contoured portion of the coversheet. An inner pedestal probe is placed on the dual wall turbinestructure such that a conductive electric path is formed from the coversheet probe to the inner pedestal probe through the cover sheet andpedestal of the dual wall structure. The cover sheet probe and innerpedestal probe apply a localized pressing force to the pedestal and thecover sheet. Electric power is applied along the conductive electricpath to heat a junction between the cover sheet and pedestal. The flowof electricity generates heat which is used to form a metallurgical bondeither by melting the interface thus creating a bond; diffusing thematerial of the components together to form a diffusion bond; or byusing a preplaced interface material that either diffuses into bothfaces and creates a diffusion bond or melts and creates a braze joint.The heated junction may cool and fixedly join, or bond, the cover sheetto the core via the pedestal.

One unique feature of the system described below may be that localizedbonding can take place. For example, individual pedestals may be locallybonded and/or defined groups or areas of pedestals may be locallybonded. The localized bonding allows for repair or rework to dual wallstructures. The localized bonding process may allow for reducedmanufacturing operation time and cost as compared to conventionalmethods such as brazing.

Another interesting feature of the system may be that the cover sheetprobe may match and/or conform to the three dimensional contour of theouter surface of the cover sheet and/or pedestal so that a path ofrelatively lower resistance may be created between the cover sheet andthe cover sheet probe. The contoured tip of the cover sheet probe andthe pressing force applied by the cover sheet probe may help create apath of relatively lower resistance between the cover sheet and thecover sheet probe by increasing the conductivity between the cover sheetand cover sheet probe relative to a junction between the inner surfaceof the cover sheet and the pedestal. This may allow for the area ofhighest resistance between the cover sheet probe and the inner pedestalprobe to be the area of contact between the cover sheet and thepedestal, creating a maximum temperature junction.

Another interesting feature may be that the inner pedestal probe isshaped so as to fit within specific areas of the dual wall structure,such as between the cover sheet and the core next to the pedestal. Thisway, predetermined areas of the airfoil can be bonded or repairedwithout affecting other areas of the structure.

FIG. 1 shows an example of a gas turbine engine 100. In some examples,the gas turbine engine 100 may be used for flight operations, forexample to supply power to and/or provide propulsion of an aircraft. Theterm aircraft, for example, may include a helicopter, an airplane, amissile, an unmanned space vehicle, or any other similar device.Alternatively or in addition, the gas turbine engine 100 may be used inother vehicles or in an industrial application. Industrial applicationsmay include, for example, an energy application, a power plant, apumping set, a marine application, a weapon system, a security system, aperimeter defense or security system.

The gas turbine engine 100 may include an intake section 120, acompressor section 160, a combustion section 130, a turbine section 110,and an exhaust section 150. Operation of the gas turbine engine 100 mayinclude receiving fluid, such as air, from the intake section 120. Thefluid may travel along the direction Dl. The fluid may travel from theintake section 120 to the compressor section 160, where the fluid iscompressed. The compressed fluid may be mixed with fuel in thecombustion section 130. The mixture of fuel and fluid may then be burnedin the combustion section 130 creating combustion gases. The combustiongases, or combustion fluid, may then flow from the combustion section130 to the turbine section 110 to extract energy from the combustionfluid. The energy from the combustion fluid may cause a shaft 140 of aturbine 114 in the turbine section 110 to rotate. The shaft 140 of theturbine 114 may in turn drive the compressor section 160. After passingthrough the turbine section 110, the combustion fluid may be dischargedfrom the exhaust section 150.

During operation of the gas turbine engine 100, the fluid, such as air,may pass through the turbine section 110. The turbine section 110 maycontain a plurality of adjacent gas turbine blades 112 coupled to arotor disk. It is understood that gas turbine blades and vanes are oftenreferred to as airfoils. In an example, the blades 112 may be bonded tothe rotor disk to form a mechanically robust, monolithic component. Theblades 112 may, alternatively, be fabricated separately from the rotordisc and the conventionally joined to the rotor disc. The blades 112 maybe made of a rigid material, for example, the blades 112 may include ametal alloy. Alternatively, the blades 112 may include a heat resistantsuper alloy composition, for example, a nickel based or cobalt basedcomposition. Alternatively, the blades 112 may include a ceramicmaterial, such as a ceramic-matric composite (CMC) material. At least aportion of the blades may be formed, for example, through a castingprocess.

In the turbine section 110, the combustion fluid may pass betweenadjacent blades 112 of the turbine 114. The combustion fluid passingover the blades 112 may cause the turbine 114 to rotate. The rotatingturbine 114 may turn the shaft 140 in a rotational direction D2, forexample. The blades 112 may rotate around an axis of rotation, which maycorrespond to a centerline X of the turbine 114 in some examples. Inaddition, or alternatively, in other examples, the blades 112 may bepart of a static vane assembly in the turbine section 110 of the gasturbine engine 100.

FIG. 2 illustrates an example of three dimensional (3D) contoured dualwalled airfoil structure in the form of a portion of blade 112 and/orvane. The features and functionality described with respect to FIG. 2may also be typical of other dual walled structures having 3D contouredsurfaces, such as other 3D contoured dual walled gas turbine enginecomponents, so the description herein should not be construed as limitedto turbine blades. The example blade 112 is illustrated as a dual wallturbine blade. The illustrated portion of the blade 112 includes a core210 and a cover sheet 220. The cover sheet 220 and core 210 may form anairfoil of the blade 112 when bonded together. The core 210 and thecover sheet 220 may, for example, be metallurgically bonded as describedherein. The core 210 and cover sheet 220 may be made of rigid materials,for example, a metal alloy. Alternatively, the core 210 and cover sheet220 may comprise a heat resistant super alloy composition, for example,a nickel based or cobalt based composition. The core 210 and cover sheet220 may be made of the same or different materials.

The blade 112 may have a highly contoured shape. For example, the blade112 may be three dimensionally contoured. The core 210 and/or coversheet 220 may have corresponding highly contoured surfaces, for example,predetermined three dimensional contoured surfaces in order to realizethe desired shape of the blade 112. A three dimensional contouredsurface refers to a surface defined by an X, Y, and Z axis. A threedimensional contoured surface is pre-defined by a cloud of points wherein addition to surface variation of X and Y coordinates, Z coordinatesmay also vary from point to point of the three dimensional surface inorder to form a predetermined three dimensioned contour. Thus, a threedimensional contoured surface may have a predetermined varying depthcomponent (e.g. Z coordinates). In contrast, a two dimensional surfacemay be defined by only an X and Y axis because Z coordinates on thesurface do not change or change only slightly with insignificant orminimal variation due to non-predefined distortions of the surface, suchas surface roughness. A two dimensional surface may have a predeterminedconstant depth, or substantially constant predetermined depth thatvaries due to the presence of surface roughness. Thus, as describedherein, predetermined three dimensionality of a contoured surface doesnot include surface roughness.

The core 210 may be formed, for example, through casting. The core 210may have a discontinuous surface. The core 210 may include a leadingedge 214, a trailing edge 218, a pressure side 234, and a suction side232. The core 210 may be hollow and include a cooling channel 240 thatextends through at least a portion of the length of the blade 112. Inthe illustrated example, the core 210 includes multiple cooling channels240 in an airfoil core of the core 210. In other examples, additional orfewer cooling channels 240 may be present. The cooling channels 240 maybe defined by one or more interior walls 242 of the core 210. Thecooling channels 240 may be supplied with fluid, such as secondary airprovided by the gas turbine engine. The core 210 may include one or morepedestals 212. The pedestal 212 may be a raised surface feature of thecore 210. The pedestals 212 may be raised from the interior wall 242 ofthe core 210. The pedestals 212 may be raised from the opposite surfaceof the interior wall 242 with respect to the cooling channel 240 so asto extend away from the interior wall 242.

FIG. 2 and the discussion herein focuses on bonding the cover sheet 220and the pedestal(s) 212 using the system and methods described.Alternatively, or in addition, the bonding performed as discussed anddescribed herein may occur between the pedestal(s) 212 and the core 210.Thus, in some examples, the pedestals 212 may be coupled with the core210 or the cover sheet 220 by other than operation of the system. Forexample, the pedestals 212 may be integrally formed with the core 210such as by casting, additive manufacture, bonding, or other joiningtechniques of the core 210 and the pedestals 212 to provide a relativelylow resistance junction, or no junction, between a respective pedestal212 and the core 210 resulting in a highly conductive path for electriccurrent. In alternative examples, the bonding performed with the systemas discussed and described herein may be between the three dimensionalcontoured surface(s) of the pedestal(s) 212 and the core 210, and thebonding of the pedestal(s) 212 and the cover sheet 220 may also beaccomplished to form the relatively low resistance junction, or nojunction, between the cover sheet 220 and the pedestal(s) 212. Anadvantage of omitting the bond between the pedestals 212 and the coversheet 220, for example, when the dual walled structure is used as aturbine blade or vane, is to avoid placing a bond created by the systemin a region that experiences higher heat during the operation of aturbine engine. It should nevertheless be understood that bonding of thethree dimensional highly contoured surface of the pedestal(s) 212 to thecover sheet 220, the core 210, or both, may be performed as describedherein.

The core 210 may include one or more pedestals 212, for example, thecore 210 may include approximately 1,000 pedestals on each side of thecore 210. The pedestals 212 may constitute surface regions of thediscontinuous surface of the core 210. The core 210 may include flowchannels 216. The flow channels 216 may be adjacent to the pedestals212, such that the pedestals 212 separate the flow channels 216. Theflow channels 216 may be positioned between the core 210 and the coversheet 220 when the core 210 and cover sheet 220 are bonded together. Theflow channels 216 may be sealed when the core 210 and cover sheet 220are bonded together, thus enabling the ability of guiding fluid througha predesignated circuitous path. Fluid, such as air, may flow throughthe flow channels 216 of the core 210.

The core 210 may include a network of pedestals 212 and flow channels216. The pedestals 212 and the flow channels 216 may form one or morepatterns of the pedestals 212 on the core 210. The interior wall 242 mayinclude inlet ports 244 that penetrate the interior wall 242. The flowchannels 216 may be in fluid communication with the cooling channel 240via the inlet ports 244. The pedestals 212 and the flow channels 216 maybe formed, for example, through a casting process. Alternatively or inaddition, the pedestals 212 and the flow channels 216 may be formed, forexample, through a machining process.

The arrangement of pedestals 212 and flow channels 216 shown in FIG. 2is only one example of a possible configuration, and is not intended tobe limiting. The pedestals 212 and the flow channels 216 may formstraight, linear paths with sharp angles. Alternatively, the pedestals212 and flow channels 216 my form curved, nonlinear paths.

The pedestals 212 may vary in shape. The pedestals 212 may be elongatedsuch that the pedestals 212 continuously extend from the trailing edge218 to the leading edge 214 of the core 210 to form the flow channels216 there between. For example, the pedestals 212 may each be in theshape of a raised rib or rectangle shaped platform. Additionally oralternatively, the pedestals 212 may be in any intermixed arrangement ofshapes and/or patterns to achieve the functional results desired of thefinal component design In one example, each rectangular pedestal 212 maycontinuously extend horizontally across the surface of the core 210,between the leading edge 214 and the trailing edge 218. For example, thepedestals 212 may be positioned parallel to each other and be spaced apredetermined distance from each other. The spacing between the parallelpedestals 212 may be the same. Alternatively the pedestal 212 may extendin differed directions with respect to each other and/or be variablyspaced from each other to form the flow channels 216. Alternatively oradditionally, the pedestals 212 may continuously extend vertically fromthe radially outward end of the core 210 to the radially inward end ofthe core 210. The vertically extending pedestal 212 may cross or connectwith one more pedestals 212 extending horizontally 212.

The pedestals 212 may connect to each other, that is, one pedestal 212may connect to an adjacent pedestal 212. The pedestals 212 may beshapes, for example circles or squares, that do not connect to eachother, that is one pedestal 212 does not contact another pedestal 212 toprovide a flow channel 216 there between. The distance between thepedestals 212 or the spacing of the pedestals 212 from each other mayform a pattern of the pedestals 212 on the core 210. The pattern mayinclude pedestals 212 uniformly spaced from each other to form arepetitive pattern, or pedestals 212 with varying spacing from eachother. Additionally or alternatively, the pattern may include pedestals212 of uniform or varying shapes.

The pedestals 212 may include a surface area 250 disposed towards thecover sheet 220. The surface area 250 of the pedestals 212 may be acontinuously connected surface area 250 of multiple pedestals 212 inexample configurations where one pedestal 212 is connected to anotherpedestal 212. The surface area 250 may abut an inner surface 224 of thecover sheet 220. The surface area 250 may be the surface of thepedestals 212 opposite the end of the pedestal 212 abutting the interiorwall 242 of the core 210. The surface area 250 may be planar.Alternatively, the surface area 250 of the pedestals 212 may becontoured.

The surface area 250 of the pedestals 212 may be uniform or may bevariable to align with an interior surface of the coversheet 220 forpurposes of bonding at least some of the pedestals 212 to the coversheet220. The surface area 250 may conform to the cover sheet 220. Forexample, the cover sheet 220 and the surface area 250 may be curved witha predetermined mathematically defined curvature such that the suctionside 232 and/or the pressure side 234 of the airfoil is formed by thecover sheet 220 when bonded to the core 210. The surface area 250 of thepedestal 212 may match the corresponding mathematically definedcurvature of the surface of the cover sheet 220 such that the coversheet 220 maintains the predetermined shape when bonded to the pedestal212, or the cover sheet 220 assumes the predetermined mathematicallydefined curvature when bonded to the pedestal 212. Accordingly, thesurface areas 250 may be one or more predetermined shapes orconfigurations to achieve desired bonding. The surface area 250 of thepedestal 212 may be highly contoured. For example, the surface area 250may be a three dimensional contoured surface formed with predeterminedX, Y and Z coordinates. The 3D contour of the surface area 250 maycorrespond with the 3D contour of an area of cover sheet 220 that thesurface area 250 contacts. The three dimensional contour of each of thesurface areas 250 may differ and/or be unique. The cover sheet 220 maybe three dimensionally contoured such that the surface area 250 of eachpedestal 212 varies and/or is different among different pedestals 212.In other words, the three dimensional contoured inner surface of thecover sheet 220 and the three dimensional contoured surface of thepedestal 210 may provide uniform intimate contiguous contacttherebetween. Alternatively or in addition, as discussed herein, thebonding of three dimensional contoured surfaces may occur between thepedestal(s) 212 and the core 210.

The cover sheet 220 may include an outer surface 222 and the innersurface 224. The inner surface 224 may be the surface of the cover sheet220 disposed towards the core 210. The inner surface 224 of the coversheet 220 may abut the pedestals 212. The inner surface 224 may becoupled to pedestals 212 when the cover sheet 220 is bonded with thecore 210 and/or the pedestals 212. The cover sheet 220 may bemetallurgically bonded to the pedestals 212 as described herein. Thecover sheet 220 may be bonded to the pedestals 212 at the surface area250. The cover sheet 220 may be bonded to the core 210 such that thecover sheet 220 covers the pedestals 212 and flow channels 216. Thecover sheet 220 may create a fluid tight seal with the pedestals 212such that fluid flows through the flow channels 216 of the core 210. Thecover sheet 220 may form a continuous outer layer of at least part ofthe blade 112. Additionally, an area of the cover sheet 220 may bebonded to another area of the cover sheet 220. For example, the coversheet 220 may be bonded to itself at the leading edge 214 and/or thetrailing edge 218 of the core 210. The outer surface 222 may be thesurface of the cover sheet 220 opposite the inner surface 224. The outersurface 222 and/or inner surface 224 may be planar or contoured. Forexample, the outer surface 222 and/or inner surface 224 may be a threedimensional contoured surface. The three dimensional contour of theouter surface 222 and the three dimensional contour of the inner surface224 may be oppositely contoured surfaces, whereas a convex outer surfaceand a concave inner surface are oppositely contoured surfaces. Forexample, a portion of a sheet with a convex outer surface would have acorresponding, oppositely contoured concaved inner surface. The coversheet 220 may include outlet ports 226 that penetrate the cover sheet.Fluid, such as air, may discharge from the flow channels 216 via theoutlet ports 226 and into the turbine section 110 (FIG. 1 ).

FIG. 3 illustrates an example of a bonding system 300. The bondingsystem 300 may include controller circuitry 340, a resistance welder350, a cooling system 360, and a press system 380. The resistance weldermay be used for bonding, for example resistance bonding, diffusionbonding, or braze bonding/brazing. A resistance bond may result in, forexample a resistant weld or weld nugget. The resistance welder 350 mayinclude a power supply 352, a cover sheet probe 310, and a innerpedestal probe 320. The resistance welder 350 may be electricallycoupled to the cover sheet probe 310 and the inner pedestal probe 320.The resistance welder 350 and the press system 380 may cooperativelyoperate in combination with the controller circuitry 340 and/or thecooling system 360. The cover sheet probe 310 may include a tip 312 andthe inner pedestal probe 320 may include a sink electrode 322 having atip 324.

The cover sheet probe 310 may be, for example, a source electrode or asupply electrode configured to supply a voltage and current. The innerpedestal probe 320 may be electrically coupled to the sink electrode322. Alternatively, the inner pedestal probe 320 may be some other formof connection to the core 210, for example, a clamp. The tip 312 of thecover sheet probe 310 and the tip 324 of the sink electrode 322 of theinner pedestal probe 320 may be made out of a conductive material, forexample an alloy. The alloy, for example, may include one or more ofcopper, cobalt, tungsten, nickel, or another similar material to, forexample, tailor a balance between thermal conductivity andcompliance/creep. The tip 312 of the cover sheet probe 310 and the tip324 of the inner pedestal probe 320 may be made of the same or differentmaterials. The parameters used for conducting the process may beadjusted to produce the type of bond desired (e.g. resistance bond,braze bond, or diffusion bond). The controller circuitry 340 may controloperation parameters 342 of the bonding system 300. The operationparameters 342 control the bonding process. The operation parameters 342may, for example, include pressing force 370, location 372, electricalcurrent 346, electrical voltage 348, cooling fluid temperature 376,sensor circuitry 378 and/or any other operational parameters used tocontrol the bonding process. The operation parameters 342 may includehardware or some combination of hardware and software to perform thedescribed functions. For example, the controller 340 may control thevoltage and current levels of electrical power supplied by theresistance welder 350 to the cover sheet probe 310 In this example, thecontroller 340 may control the electrical current 346 and/or theelectrical voltage 348 supplied to the cover sheet probe 310 based onpredetermined settings, user entered values, or sensed feedback providedfrom the sensor circuitry 378. The operation parameters 342 may varydepending on the operation, but may, for example, be set to a pressingforce 370 of 1779.29 Newtons, a specific pedestal location 372, anelectrical current 346 of 1630 Amps, and a cooling fluid temperature 376of room temperature. The pressure and temperature sensor circuitry 378and/or any other operational parameters may also be used to control thebonding process. The resistance welder 350 may, for example, be aMiyachi Unitek 875 Dual Pulse Stored Energy Power Supply. Parameters ofthe resistance welder 350 may vary depending on the materials,conditions, operation, and other variables, but may, for example, be setto the parameters in Table 1.

TABLE 1 Preheat Start Up-Slope Bonding Squeeze Force Preheat TimeUp-Slope Time Current BondingTime 90 1779.29N 30% 60-90 30% 60 50-70%30-60 cycles cycles cycles cycles

The controller circuitry 340 may include at least one processorcircuitry 344 in communication with memory storage circuitry 374. Atleast some of the functionality of the controller circuitry 340 asdescribed herein may be performed with the processor circuitry 344. Forexample, the processor circuitry 344 may access and store predeterminedsettings for at least some of the operation parameters 342 in memorystorage circuitry 374. In addition, or alternatively, otherfunctionality of the bonding system 300 may be provided by other partsof the controller circuitry 340. For example, the controller circuitry340 may control the magnitude of voltage and a flow of current throughthe cover sheet probe 310 and the inner pedestal probe 320. Thecontroller circuitry 340, for example, may control the supply of voltageand current to the cover sheet probe 310 such that an intermittent pulseof electric power is supplied to the cover sheet probe 310 The durationand magnitude of the intermittent pulse of electric power may becontrolled by the controller circuitry 340. A practical application ofthis capability, for example, is interpreting Non-Destructive Testing(NDT) or Non-Destructive Evaluation (NDE) data to determine the numberof pedestals or area requiring bonding repair and selecting theappropriate cover sheet probe 310 based on this data and the associatedpresent bonding parameters 342. Portions of the cover sheet 220 thatabut a pedestal 212 and/or each pedestal 212 may have a uniquepredetermined three dimensional contoured surface. Each portion, area,or sub-area of the three dimensional contour of the cover sheet 220and/or pedestal 212 may correspond to a specific cover sheet probe 310Alternatively, or in addition, each portion area, or sub-area of thethree dimensional contour of the of the cover sheet 220 and/or eachpedestal 212 may correspond to only one cover sheet probe 212. Thus, insome examples, the three dimensional contour of each cover sheet probe212 may correspond to only one pedestal 212 or portion of the coversheet 220. The system 300 may choose the correct cover sheet probe 212and/or set the parameters for completion of bonding based on the area orsub-area needing repair.

The sensor circuitry 378 may receive and process electric signals fromexternal sensors, such as current, voltage, pressure, temperature, andproximity sensors providing electric signals indicative of therespective sensed parameters to the controller circuitry 340 via thesensor circuitry 378. Alternatively or additionally, the sensorcircuitry 378 may receive and process signals from externally processeddata such as (NDT/NDE) sensors or results. The sensed parameters may beused by the controller circuitry 340 to control the bonding system 300in the manner described.

The sensors may detect resistance, current, bonding pressure, andtemperature, which may be provided as feedback and/or feed forwardand/or monitoring signals to the controller circuitry 340. Based on thesensed signals from the sensors, the controller circuitry 340 mayprovide close-loop adjusted parameters.

The tip 312 of the cover sheet probe 310 may be placed in contact withthe outer surface 222 of the cover sheet 220. For example, the tip 312may abut the outer surface 222 of the cover sheet 220. The tip 312 ofthe cover sheet probe 310 may be three dimensionally contoured to followor match a portion of the three dimensional contoured outer surface 222of the cover sheet 220. Additionally the tip 312 may be threedimensionally contoured to follow the 3D contoured surface area 250 ofthe pedestal 212 in contact with the 3D contoured inner surface 224 ofthe cover sheet 220. For example, the three dimensional contouredsurface of the tip 312 may have the same three dimensional contour ofthe inner surface 224 of the cover sheet 220. Additionally oralternatively, the outer surface 222 of the cover sheet 220 may have thesame three dimensional contour as the surface 250 of the pedestal 212.As the inner surface 224 and the outer surface 222 of the cover sheet220 may be oppositely contoured, the surface 250 of the pedestal 212 andthe tip 312 may be oppositely contoured such that the outer surface 222,inner surface 224, pedestal 212, and tip 312 all have matching threedimensionally contoured surfaces. The matching three dimensionalcontoured surfaces of the tip 312, outer surface 222 of the cover sheet220, the inner surface 224 of the cover sheet 220, and the pedestal maycreate a path of lower relative resistance at a first junction 328between the tip 312 and the outer surface 222 than at a second junction330 of the inner surface 224 and the surface area 250 of the pedestal212.

The three dimensional contour of the tip 312 may allow for the distancebetween tip 312 of the cover sheet probe 310 and the outer surface 222to remain constant along the first junction. The distance between theinner surface 224 of the cover sheet 220 and the surface area 250 of thepedestal 212 along the second junction may be larger than the distanceof the first junction 328. Alternatively or additionally, tip 312 of thecover sheet probe 310 and/or the tip 324 of the inner pedestal probe 320may be made of different material(s) than the cover sheet 220 and/orcore 210. The material(s) of the tips 312 and/or 324 may have a higherconductivity than the material(s) of the core 210 and/or cover sheet 220of the blade 112. For example, the tips 312 and/or 342 may be made ofcopper, or another similar material, and provide a lower resistance thanthe material(s) of the core 210 and/or cover sheet 220, for example anickel or cobalt based super alloy. The material(s) of the tips 312/324may also conform to a contacting surface better than the material(s) ofthe core 210 and/or cover sheet 220. Because of the material differencebetween the tip(s) and the blade 112 and/or because the distance may belarger between the inner surface 224 and the pedestal 212 than thebetween the tip 312 and the outer surface 222, the resistance along aconductive electrical path 314 may be highest at the second junction330. Thus, the second junction 330 may be a localized maximumtemperature junction of the conductive electric path 314, by design.

The tip 312 of the cover sheet probe 310 may include a surface areafootprint that corresponds to the surface area footprint of the pedestal212 on the opposite side of the cover sheet 220 from the tip 312. Thus,for example, a square or circular shaped footprint of a 3D contouredsurface of the tip 312 may correspond in shape to a square or circularshaped footprint of a 3D contoured surface of a pedestal. In addition,or alternatively, the surface area footprint of the tip 312 contactingthe outer surface 222 of the cover sheet 220 may be equal to or greaterthan a surface area footprint of the pedestal 212 contacting the innersurface 224 of the cover sheet 220. Thus, for example if the tip 312 ofthe cover sheet probe 310 includes a 3D contoured surface of a 3.175 mmsquare, or an area of 10.08 square mm, the 3D contoured surface of thepedestal 212 contacting the inner surface 224 of the cover sheet 220 isequal to or less than 10.08 square mm. In an example, the surface areaof the tip 312 may be larger than the surface area of a pedestal 212such the 3D contoured surface of the tip 312 extends beyond one or moreperipheral edges of the pedestal 212 by up to 30% of the total distancebetween the pedestal 212 and neighboring pedestals. Because the surfacearea of the tip 312 is larger than the surface area of the pedestal 212,there may be less resistance between the tip 312 and the outer surface222 of the cover sheet 220 than between the inner surface 224 of thecover sheet 220 and the pedestal 212. This may contribute to theresistance along the conductive electrical path 314 being highest at thesecond junction 330. Alternatively or in addition, as discussed herein,the bonding of three dimensional contoured surfaces may occur betweenthe pedestal(s) 212 and the core 210, wherein the highest resistancealong the conductive electrical path 314 is between the pedestal 212 andthe core 210.

The tip 324 of the sink electrode 322 of the inner pedestal probe 320may be in contact with a part of the dual wall turbine blade 112 such asthe core 210. For example, the tip 324 of the inner pedestal probe 320may abut a surface of the core 210, such as against one or more of thepedestals 212. Alternatively, the tip 324 may abut the interior wall242. The tip 312 of the cover sheet probe 310 may abut the cover sheet220 opposite an area where one of more of the pedestals 212 abuts theinner surface 224 of the cover sheet 220. The controller circuitry 340may control the press system 380 using the tips 312 and 324 to exert thepressing force 370 against the cover sheet 220 and the dual wall turbineblade 112, respectively. The pressing force 370, for example, may bepredetermined, user entered or based on parameters sensed by externalsensors. The pressing force 370, for example, may be localized to onepredetermined area of the airfoil without applying force to other areasof the airfoil. The cover sheet 220 may be temporarily affixed to thedual wall turbine blade 112 by the pressing force 370 or some otherretention process. The cover sheet 220 may be affixed to the dual wallturbine blade in a predetermined location or positioned in preparationfor bonding.

The tip 312 of the cover sheet probe 310 and the tip 324 of the innerpedestal probe 320, when contacting the cover sheet 220 and core 210respectively, may create a conductive electrical path 314. Electricitymay flow along the conductive electrical path 314 from the cover sheetprobe 310 to the inner pedestal probe 320. Electricity may flow alongthe conductive electrical path 314 through at least part of the dualwall structure 112. Electricity may flow along the conductive electricalpath 314 through at least part of the pedestal 212. Electricity may flowthrough the cover sheet 220 and the core 210. The flow of electricitymay heat the second junction 330 between the cover sheet 220 and thepedestal 212. The second junction 330, for example, may be createdbetween the cover sheet 220 and one or more pedestals 212. The heatgenerated by resistance in the second junction 330 to the flow ofelectricity may create a heated area 332 at the second junction 330. Theheated area 332 may cool and fixedly couple the cover sheet 220 and core210. The heated area 332 may cool to form, for example, a resistancebond or a spot bond. A resistance bond may be, for example a resistanceweld. A spot bond may be, for example, a spot weld. The bonding, forexample, may be localized. The heated area 332 may cool to form, forexample, a bond nugget, for example, a weld nugget. The bonding may belocalized to the predetermined surface area 250 (FIG. 2 ) of one or moreof the pedestals 212. Alternatively or in addition, as discussed herein,the bonding of three dimensional contoured surfaces may occur betweenthe pedestal(s) 212 and the core 210.

Additionally, the inner pedestal probe 320 may contact the core 210 at athird junction 334 with a predetermined contact surface area. A ratio ofthe contact surface areas of the third junction 334 (between the innerpedestal probe 320 and the core 210) and the first junction 328 (betweenthe cover sheet probe 310 and the outer surface 224 of the cover sheet220) may be predetermined. For example, the inner pedestal probe 320 maycontact a larger surface area of the blade 112 than the cover sheetprobe 310 By having a larger contact surface area, the third junction334 may have a lower relative resistance than other junctions along theconductive electrical path 314. The contact ratio may allow for amaximum temperature junction along the conductive electrical path 314 tobe at the second junction 330 between the inner surface 224 of thecoversheet 220 and the pedestal 212. Alternatively or additionally, thesecond junction 330 may be a maximum temperature junction as compared tothe first junction 328 or third junction 334 of a respective pedestal212 corresponding area of cover sheet 220. The first junction 330,second junction 330, and third junction 334 may be along the conductiveelectrical path 413.

The cooling system 360 may include one or more pumps 362, a heatexchanger 364, a temperature sensor 366, and supply lines 368. Thecooling system 360 may circulate a cooling fluid 378. The cover sheetprobe 310 may include a cooling passageway 316. The cooling passageway316 may extend through the cover sheet probe 310 The cooling passageway316, for example, may extend through the tip 312 of the cover sheetprobe 310 The supply lines 368 may couple to the cooling passageway 316such that cooling fluid may be circulated through the cover sheet probe310 and/or the tip 312 of the cover sheet probe 310 The cooling fluid378 may flow through the supply lines 368 to the cover sheet probe 310The cooling fluid 378 may cool the cover sheet probe 310 and bycirculating through the cover sheet probe 310 and return to the heatexchanger 364. The returning cooling fluid 378 may be cooled by the heatexchanger 364 and then again be circulated through the cover sheet probe310 The flow of the cooling fluid 378 may be driven by one or more pumps362 included in the cooling system 360. The temperature sensor 366 mayone or more temperature sensors disposed to sense the temperature of thecooling fluid 378 circulating in the cooling system 360, such as forexample in the flow path before or after the cover sheet probe 310 Thetemperature sensor 366 may sense the temperature of the cooling fluid378 being supplied to and/or received from the cover sheet probe 310 Thecontroller circuitry 340 may increase, decrease, or maintain constantthe cooling of the cover sheet probe 310 using the cooling system 360based on feedback from the temperature sensor 366. For example, thecontroller 340 may increase or decrease the flow of the cooling fluid378 by controlling flow rate with the one or more pumps 362.Alternatively, or additionally, the controller 340 may increase ordecrease the rate at which the cooling fluid 378 is cooled by the heatexchanger 364.

The press system 380 may include a pressing force generator 382, one ormore pressure sensors 384, and one or more proximity sensors 386. Theproximity sensor 386 may be used by the press system 380 to locate orotherwise position the cover sheet probe 310 in a predetermined area ofthe cover sheet 220. One application of this, for example, is in theform of interpreting NDT and/or NDE data and locating a specific coversheet probe 310 or bank of cover sheet probes 310 Another application,for example, may be operational sequencing of bank cover sheet probes310 to successfully manufacture a highly contoured component.Additionally, the proximity sensor 386 may be used to locate the innerpedestal probe 320 to a predetermined area of the core 210. For example,the proximity sensors 386 may be used to locate the inner pedestal probe320 to one of the pedestals 212 and the cover sheet probe 310 to an areaof the cover sheet 220 in contact with the corresponding pedestal 212.The pressing force generator 382 may generate a predetermined amount offorce to be applied by the cover sheet probe 310 to the cover sheet 220.For example, the cover sheet probe 310 may apply a predetermined force,measured in Newtons, to the cover sheet in a predetermined direction,such as perpendicular to the outer surface of the cover sheet. Forexample, an example of this is interpretation of NDT and/or NDE resultsand selecting a proper cover sheet probe 310 from a bank of cover sheetprobes 310 and setting the force appropriately. Another example isproper sequencing of bank cover sheet probes 310 and adjusting thepressure and parameters based on the specific cover sheet probe 310required to manufacture a highly contoured 3D component.

In one example, the bonding system 300 may include a two-axis X-Y stagewith a servo control system built to locate defect areas for resistancebonding repair. The bonding system 300 may have a machine accuracy of0.00508 mm and a travel distance of 60.96 cm×101.6 cm. The X-Y-Z systemmay be integrated with resistance bonding system and with the NDE/NDTsystem, inspection of images, and digital data.

The pressing force generator 382 may generate a corresponding pressingforce. The pressure sensors 384 may be used to detect to a magnitude offorce being applied to the cover sheet 220 by the press system 380.Feedback from the pressure sensors 384 may be used by the bonding system300 to adjust the amount of force generated by the pressing forcegenerator 382. The applied force may create an electric conductive pathof relatively less resistance between the probe 310 and the cover sheet220. One interesting feature of the bonding system 300, for example, isthat the system 300 may use resistance pre-heating and long post-bondinghold time, with a coversheet probe 310 having a predetermined 3Dcontoured surface design, and plated bonding interfaces.

The press system 380 may be controlled to balance heating of the heatedarea with cooling of the tip 312 of the cover sheet probe 310 to avoidindentation of the cover sheet 220 due to excessive temperature of thetip 312 in combination with the contacting pressure being asserted onthe cover sheet 220. For a given part there may be multiple uniqueprobes 310, the control system may perform selection of the cover sheetprobe 310 selection based on NDT, NDE, and/or other sequencing input,select the correct probe 310 and select the proper parameters based onthe probe 310 and results that are trying to be achieved.

All features and functionality discussed with reference to FIGS. 1-3 areapplicable to the following embodiments and examples unless otherwiseindicated.

FIGS. 4 and 5 illustrate examples of a probe 410. The probe 410 may beone example of the cover sheet probes 310 of the bonding system 300(FIG. 3 ). The probe 410 may, alternatively or additionally, be anexample of one or more of the inner pedestal probes 320 of the bondingsystem 300 (FIG. 3 ). The probe 410 may include a tip 412. The tip 412may be one example of tip 312 (FIG. 3 .) Thus, for brevity, thediscussion with respect to FIGS. 2-3 will not be repeated and it shouldbe understood that all described features and functionality areapplicable to FIGS. 4 and 5 unless otherwise indicated. The tip 412 mayinclude a contacting area 414. The tip 412 and/or the contacting area414 may be three dimensionally contoured to correspond to the threedimensional contoured surface area 250 of one or more of the pedestals212 (FIG. 2 ). Alternatively or additionally, the tip 412 and/or thecontacting area 414 may be three dimensionally contoured to match thesurface area 250 of one or more of the pedestals 212. Alternatively oradditionally, the tip 412 and/or the contacting area 414 may be threedimensionally contoured to match the three dimensional contour of theouter surface 222 of the cover sheet 220 (FIG. 2 ). The cover sheetprobes 310 and the inner pedestal probe 320 may have the same ordifferent shapes and/or contours. Alternatively or additionally, theprobe 410 of the inner pedestal probe 320 may be shaped, for example,such that the inner pedestal probe 320 can access and contact apredetermined area of the core 210. For, example, the sink electrode 322and inner pedestal probe 320 may be shaped such that the sink electrode322 and/or inner pedestal probe 320 can access the cooling channel 240and/or area of the interior wall 242. The sink electrode 322 and/orinner pedestal probe 320 may be shaped, for example, such that the sinkelectrode 322 and/or inner pedestal probe 320 can access the core 210already bonded to the cover sheet 220. The three dimensional contour andconformity of the tip 412, and the parameters 342 of the bonding system300, are chosen to balance the cooling aspect and tip compliance suchthat deformation of the coversheet 220 is minimized or absent. Coversheet deformation results in stress risers that can initiate cracks. Theprobe tips 412 may be manufactured, for example, by brazing, diffusionbonding, and/or ALM such that cooling liquid can flow into the distaltips 412 of the shaped probe 410 to maximize cooling. The shaped probes410 allow power selection of the bonding system 300 to balance probecompliance and cover sheet deformation to minimize or eliminate coversheet deformation. The probes 412 may be designed based on the NDTand/or NDE inspection results of defects to perform this repair inautomated settings. The software that controls the system may be linkedto code, in one example, code written in Labview, to link data comingfrom ultrasonic and/or other operations related to the NDE and/or NDT.

The surface area 250 and/or the outer surface 222 may be matched toallow for better surface contact and therefore conductivity between thesurface area 250 and the probe 410 and/or the outer surface 222 and theprobe 410. Contouring to match the tip 412 with the surface of the coversheet 220 may create a relatively low resistance conductive electricalpath between the tip 412 of the probe 410 and the outer surface 222 ofthe cover sheet 220. The conductive electrical path at the firstjunction 328, between the tip 412 and the outer surface 222, may berelatively low resistance with respect to the resistance of theconductive electrical path at the second junction 330 of the innersurface 224 and one of the pedestals 212. The highest resistance alongconductive electric path 314 (FIG. 3 ) may be at the second junction330. The magnitude of the pressing force 370 may also lower theresistance between the tip 412 and/or contacting area 420 and the outersurface 222. The probe 410 may allow localized bonding. For example, thebonding may be welding, such as resistance welding or spot welding. Thelocalized bonding may be used, for example, for repairs. For example,the repairs may repair a breach in the cover sheet 220 or to correctlocalized defects in the dual wall turbine blade 112. The defects may befound, for example, through inspection, such as radiographic, ultrasonicor thermographic inspection. The thermographic inspection may beaccomplished with, for example, an infrared (IR) camera and flash lamps.

FIG. 4 illustrates an example of a probe 410. The probe 410 may includea tip 412 having head 416 and a protrusion 418. The head 416 may be afrustoconical shaped member that is tapered toward the protrusion 418 toprovide a diminishing cross-sectional area. The protrusion 418 mayextend outwardly away from the head 416. The protrusion 418 may haveplanar sides extending to a distal end 420 of the probe 410 forming thecontacting area 414. The contacting area 414 may be a circular,triangular, rectangular or any other shaped surface, and may bedimensioned to correspond to at least a portion of the surface area 250of a pedestal 212. (FIG. 2 )

The head 416 and the protrusion 418 may be cooperatively manipulated toallow the probe 410 to access and abut otherwise unreachable areas ofthe outer surface 22 or the core 210 to perform bonding. In otherexamples, the contacting area 414 may be one or more of the planarsurfaces of the protrusion 418. The protrusion 418 may be anelectrically conductive material through which electrical power suppliedby the resistance welder 350 may flow. The head 416 may be anon-conductive heat dissipating member surrounding the protrusion 414.In other examples, the head 416 may be an electrically conductivematerial through which electrical power supplied by the resistancewelder 350 may flow.

The head 416 may be coupled with an insulator 422 by a neck joint 424.The insulator 422 may be formed of a non-conductive material thatdissipates heat generated by current flowing through the probe 410. Theneck joint 424 may fixedly couple the insulator 422 and head 416. Theinsulator 422 may also include a portion of the cooling passageway 316(FIG. 3 ) included in the probe 410.

The probe 410 may also include an attachment end 430. The attachment end430 may include a threaded member 432, a flange 434 and a bolt 436. Thethreaded member 432 may threadably couple with structure such as an arm,strut or other member through which the pressing force 370 may beexerted on the probe 410 by the pressing system 380. (FIG. 3 ) Thethreaded member 432 may be formed to include at least one aperture 438through which the cooling fluid may flow into the cooling passageway 316(FIG. 3 ) included in the probe 410. In an example, the aperture 438 mayinclude an inlet and an outlet to provide circulation through the probe410. The flange 434 may include a conical shaped end 440 to create aliquid tight seal with structure to which the threaded member 432 isdetachably coupled. The bolt 436 may provide a grip location forrotationally removing and installing the probe 410 using a tool such asa wrench. FIG. 5 illustrates another example of a probe 410. The probe410 of this example includes a tip 412 and an attachment end 430. Inthis example, the tip 412 may include a head 416, but not include aprotrusion 418 (FIG. 4 ). Additionally or alternatively, the probe 410may not include the cooling passageway 316. For example, the tip 412 maybe solid without any internal passageways for cooling fluid 378. Thesurface of the probe 410 may be a curved surface, for example a domeshaped surface. The contacting area 414 may be disposed on any portionof the surface of the curved tip 412. The surface of the contacting area414 may be three dimensionally contoured to match the surface area 250of the pedestal 212 and/or the outer surface 222 of the cover sheet 220.The attachment end 430 may be a solid rigid shaft configured to befixedly held in a compression fitting, such as a chuck. The compressionfitting may be included in a structure such as an arm, strut or othermember through which the pressing force 370 may be exerted on the probe410 by the pressing system 380. (FIG. 3 )

FIGS. 6 and 7 illustrate examples of a portion of the bonding system 300and a cut-away view of a three dimensional (3D) contoured dual wallstructure. The bonding system 300 may be used to initially bond thecover sheet 220 and the core 210 to form a structure, such as a newairfoil. The bonding system 300 may simultaneously abut a correspondingtip 312 to each predetermined area of the cover sheet 220, such thateach predetermined area of the cover sheet 220 aligns and abuts with oneof the pedestals 212. The bonding system may then, at substantially thesame time, bond the cover sheet 220 to the pedestals 212 at each secondjunction 330 of the cover sheet 220 and pedestals 212, such that aconductive electrical path 314 is formed between each tip 312 andrespective pedestal 212, wherein each second junction 330 of the coversheet 320 and core 310 may be a respective maximum temperature junction.Each conductive electrical path 314 may include a first junction 328,second junction 330, and third junction 334. Additionally, oralternatively, the bonding system 300 may be used to selectively repairan area of a pre-existing airfoil, such as to create or repair a bondbetween a single second junction 330 or preselected second junctions 330of one of the pedestals 212 and the corresponding areas of the coversheet 220. The bonding system may abut the tip 312 of the cover sheetprobe 310 to a single area of the cover sheet 220, wherein the area ofthe cover sheet 220 abuts to one of the pedestals 212. The bondingsystem 300 may abut the tip 312 of the sink probe 322 to a predeterminedarea of the core 210 corresponding to the pedestal 212. The bondingsystem 300 may then create a bond at the single predetermined secondjunction 330 of the pedestal 212 and the cover sheet 220. Accordingly,in a repair mode, the processor circuitry 340 may selectively energizeonly some of the cover sheet probes 310 where a bonding repair isdesired. Alternatively or in addition, as discussed herein, the bondingof three dimensional contoured surfaces may occur between thepedestal(s) 212 and the core 210.

FIG. 6 illustrates another example of a portion of the bonding system300 and a cut-away view of a 3D contoured dual wall structure. One ormore of the cover sheet probe 310 may each include a plurality of thetips 312. For example, multiple tips 312 may be coupled to the samecover sheet probe 310, as illustrated. The plurality of tips 312 mayform a pattern of tips 312. The core 210 may include a plurality of thepedestals 212. The pedestals 212 may form a pattern of the pedestals212. One or more of the tips 312 may abut against the outer surface 222of the cover sheet 220. For example, one or more of tips 312 may abutagainst the outer surface 222 such that each one of the tips 312 matchto one of the pedestals 212. The pattern of the pedestals 212 may matchthe pattern of tips 312 such that a location of each one of the tips 312on the outer surface 222 corresponds to a location of each one of thepedestals 212 on the core 210. For example, the cover sheet probe 310may include a tip 312 for each of the second junctions 330 of the coversheet 320 and core 310.

FIG. 7 illustrates another example of a portion of the bonding system300 and a 3D contoured dual wall structure. One cover sheet probe 310may include tips 312 for only a portion of the second junctions 330. Forexample, one or more pull planes 710 of the core 210 may be determinedbased on the 3D contour of the core 210 and blade 212, for example,based on the degree of pull angle or draft built into the core 210and/or blade 212. The pull planes 710 may corresponded to a portion ofthe 3D surface of the core 210, wherein a plurality of pedestals 212 maybe packaged within one pull plane 710. The 3D contoured surface of thecover sheet probe 310 may correspond to the pull plane 710, wherein eachone of the tips 312 of a single cover sheet probe 310 corresponds to arespective pedestal 212 within the pull plane 710. The bonding system300 may include cover sheet probes 310 each corresponding to arespective pull plane 710 of the core 210, wherein each probe 310includes a plurality of tips 312. Each tip 312 may correspond to arespective pedestal 212 and the three dimensional contoured surface ofthe tip 312 corresponding to the three dimensional contoured surface ofthe pedestal 212.

In a new manufacturing operating mode, the tips 312 may simultaneouslybe energized while abutted to the outer surface 222 such that thebonding system 300 simultaneously creates a bond at each second junction330 of the cover sheet 220 and core 210. Additionally or alternatively,in a repair operating mode only selected of the tips 312 may beenergized while abutted to one or more second junctions 330 such that abond is created at only a portion of the second junctions 330 of thecore 210 and cover sheet 220. Selection of the tips to energize may beuser selected, or may be selected based on testing to identify existingbonds in need of repair.

One or more of the inner pedestal probe 320 may be placed on the core210 to allow for conductive electrical paths 314 to form between theinner pedestal probe 320 and each tip 312 of the cover sheet probe 310For example the inner pedestal probe 320 may be placed at apredetermined area of the core 210 to allow for bonds to be createdsimultaneously at each second junction 330 of the core 210.Alternatively or additionally, the inner pedestal probe 320 may beplaced, for example, in an internal passage of the core 210corresponding to one or more of the pedestals 212 to allow for bonds tobe created at only a portion of the second junctions 330 of the core210. For example, the inner pedestal probes 320 may be inserted in tothe cooling channel 240 or flow channel 216. For example, the innerpedestal probe 320 may be inserted into the cooling channel 240 andcontact a portion of the interior wall 242. The inner pedestal probe 320may contact a portion of the interior wall 242 corresponding to one ormore of the pedestals 212. Alternatively or in addition, as discussedherein, the bonding of three dimensional contoured surfaces may occurbetween the pedestal(s) 212 and the core 210.

FIG. 8 illustrates still another example of a portion of the bondingsystem 300 and a cut-away view of a 3D contoured dual wall structure.Each one of the plurality of cover sheet probes 310 may include acorresponding one of the tips 312. The core 210 may include a pluralityof the pedestals 212. The plurality of cover sheet probes 310 may form apattern. The pattern of the cover sheet probes 310 may match a patternof pedestals 212. The corresponding tip 312 of each one of the coversheet probes 310 may abut against the outer surface 222 of the coversheet 220. The corresponding tip 312 of each one of the cover sheetprobes 310 may each align with one of the pedestals 212. One or more ofthe inner pedestal probes 320 may abut a predetermined area of the core310 to create the conductive electrical path 314 through the core 210from the cover sheet probes 310 The inner pedestal probes 320 may alignwith an area of the core 210 abutting the inner surface 224 of the coversheet 220 opposite the outer surface 222 abutted to the cover sheetprobe 310 The inner pedestal probe 320 may, for example, be placed inthe cooling channel 240 of the core 210 such that the inner pedestalprobe 320 contacts the portion of the inner wall 242 opposite a locationof one of the pedestals 212 being coupled with the interior wall 242.

FIG. 9 illustrates yet another example of a portion of the bondingsystem 300 and a cut-away view of a 3D contoured dual wall structure. Atemporary shielding material 810 may be applied to the dual wall turbineblade 112. The temporary shielding material 810 may be used to furthercontrol the bonding process. The temporary shielding material 810 mayhelp control the bonding process such that localized repair and/orrework can be done on one area the dual wall turbine blade 112 withoutaffecting other areas of the dual wall turbine blade 112. For example,the temporary shielding material 810 may be applied to protect areas ofthe dual walled turbine blade 112, for example an area of the core 210and/or the cover sheet 220, from the heat generated by the bondingprocess. For example, the temporary shielding material 810 may beapplied adjacent to one or more of the pedestals 212. The temporaryshielding material 810, for example, may be applied in one or more ofthe flow channels 216 on either side, or surrounding, one of more of thepedestals 212. The pedestals 212 may correspond to an area of the coversheet 220 in contact with one or more of the tips 312 of one or more ofthe cover sheet probes 310 The temporary shielding material 810 may bemade of an insulating material. For example, the temporary shieldingmaterial 810 may be ceramic. The temporary shielding material 810 may beremoved after the bonding process is complete, for example, when thecover sheet probes 310 and inner pedestal probes 320 have been removedfrom the core 210 and cover sheet 220. The temporary shielding material810 may be removed, for example, by a mechanical process such asdrilling or pressure washing. Alternatively or additionally, thetemporary shielding material 810 may be removed through a heatingprocess to burn of or liquefy the temporary shielding material 810,and/or a chemical process such application of a solvent to dissolve thetemporary shielding material 810.

FIG. 10 illustrates still another example of a portion of the bondingsystem 300 and a cut-away view of a 3D contoured dual wall structure. Anadhesive 910 and/or a braze material 920 may be applied to the dual wallturbine blade 112. The adhesive 920 may be controllably applied to thecore 210, for example, to one of more of the pedestals 212. Prior toapplying the adhesive 910, the pedestals 212 may undergo standardcleaning and/or grinding procedures to remove contaminants such as dust,chemical residues, oxides or other compounds that could interfere withthe bonding process. The adhesive 910 is contacted with and selectivelydeposited onto the pedestals 212. The adhesive 910 may be deposited onlyon the surface of the pedestals 212. The adhesive may additionally onlybe deposited on pre-selected pedestals 212. The adhesive 910 has asufficient viscosity to be a self-supporting layer without flowing intothe flow channels 216. The adhesive 910 may be applied by a rolling abelt or roller coated with the adhesive 910. The layer of adhesive 910is controllably and uniformly deposited on to the pedestals 212 with amass density (mass per unit area) that may lie in a range from about0.001 g/in² to about 0.050 g/in², with a preferred range of 0.002 g/in²to 0.010 g/in². The range and preferred range may depend upon thecomposition and viscosity of the adhesive 910. The pedestal 212 shapeand contour of the airfoil may also contribute to the range. A brazematerial 920 may be applied over the layer of adhesive 910. The brazematerial 920 may include a metal alloy. The composition of the brazematerial 920 may be selected based on the materials of the dual wallturbine blade 112, for example, such as the materials from which thecore 210 and/or the cover sheet 220 are made. The braze material 920 isapplied such that the braze material attaches to the adhesive 910. Apredetermined amount of braze material 920 may be applied.

The braze material 920 may or may not be heated before the bondingprocess. By not heating the braze material 920 prior to the bondingprocess, operation costs and time may be reduced. However, the brazematerial 920 may be heated to a suitable temperature to adhere the brazematerial 920 to the core 210. For example, the braze material 920 may beheated to a sintering temperature. For example, the sinteringtemperature may be high enough to sinter the braze material 920, but lowenough to avoid melting the braze material 920. The temperature may bein the range of approximately 55.6° C. below the solidus to 16.7° C.above the liquidus of the braze material 920. The liquidus is the lowesttemperature at which the braze material is completely liquid, and thesolidus is the highest temperature at which the braze material iscompletely solid. The temperature range may vary depending on thematerial used for the braze material 920. After heating, the brazematerial 920 may be attached to the core 210.

The cover sheet 220 may then contact the core 210, for example the coversheet 220 may contact one or more of the pedestals 212. The cover sheet220 may be held fixedly in place by the cover sheet probe 310 applyingthe pressing force 370. The applied pressing force 370 may then compressthe adhesive 910 and the braze material 920. The adhesive 910 and thebraze material 920 may be compressed between the surface area 250 of theone or more pedestals 212 and the corresponding inner surface 224 of thecover sheet 220. Electricity may then be applied along the conductiveelectrical path 314 between the cover sheet probe 310 and the innerpedestal probe 320. The electricity may generate heat along theconductive electrical path 314. The heat may liquate the braze material920. The heat may liquate the surface area 250 of the one or morepedestals 212 in contact with the braze material 920. The heat from theflow of electricity and the pressing force 370 may bond the core 210,for example the one or more pedestals 212, with the cover sheet 220. Thecore 210 and the cover sheet 220 may be bonded by a resistance bonding.Alternatively or in addition, as discussed herein, the bonding of threedimensional contoured surfaces may occur between the pedestal(s) 212 andthe core 210. After the bond process, the joint of the braze material920 and the surface area 250 of the pedestal 212 may beindistinguishable from the rest of the core 210. One advantage of thisprocess may be the small amount of braze material 920 used as comparedto conventional brazing processes. The predetermined amount of brazepowder 114 adhered to the pedestals 212 may lie in a range from about0.04 g/in² to about 0.25 g/in², with a preferred range of about 0.06g/in² to about 0.08 g/in². The brazing process may be done in air, aprotective atmosphere, and/or in a vacuum.

Alternatively or additionally, a preplaced interface material, forexample an interlayer assist material, may be heated by the electricitythat passes through the interface of the pedestal 212 and cover sheetinterface 220. This heated, preplaced material either diffuses into boththe inner surface 224 of the cover sheet 220 and the surface area 250 ofthe pedestal 212 to create a diffusion bond or melt and create a brazejoint. The preplaced material can be, for example, in the form of powderor foil. The preplaced material composition may be, for example, analloy or pure element depending upon the base material and the type ofbonding desired. The atmosphere the bonding will be conducted in dependsupon the type of material being utilized and the intended results. Theatmosphere, for example, may range from air to any other conceivableatmosphere providing the benefits desired.

The methods, devices, processing, circuitry, and logic described abovemay be implemented in many different ways and in many differentcombinations of hardware and software. For example, all or parts of theimplementations may be circuitry that includes an instruction processor,such as a Central Processing Unit (CPU), microcontroller, or amicroprocessor; or as an Application Specific Integrated Circuit (ASIC),Programmable Logic Device (PLD), or Field Programmable Gate Array(FPGA); or as circuitry that includes discrete logic or other circuitcomponents, including analog circuit components, digital circuitcomponents or both; or any combination thereof. The circuitry mayinclude discrete interconnected hardware components or may be combinedon a single integrated circuit die, distributed among multipleintegrated circuit dies, or implemented in a Multiple Chip Module (MCM)of multiple integrated circuit dies in a common package, as examples.

Accordingly, the circuitry may store or access instructions forexecution, or may implement its functionality in hardware alone. Theinstructions may be stored in a tangible storage medium that is otherthan a transitory signal, such as a flash memory, a Random Access Memory(RAM), a Read Only Memory (ROM), an Erasable Programmable Read OnlyMemory (EPROM); or on a magnetic or optical disc, such as a Compact DiscRead Only Memory (CDROM), Hard Disk Drive (HDD), or other magnetic oroptical disk; or in or on another machine-readable medium. A product,such as a computer program product, may include a storage medium andinstructions stored in or on the medium, and the instructions whenexecuted by the circuitry in a device may cause the device to implementany of the processing described above or illustrated in the drawings.

The implementations may be distributed. For instance, the circuitry mayinclude multiple distinct system components, such as multiple processorsand memories, and may span multiple distributed processing systems.Parameters, databases, and other data structures may be separatelystored and managed, may be incorporated into a single memory ordatabase, may be logically and physically organized in many differentways, and may be implemented in many different ways. Exampleimplementations include linked lists, program variables, hash tables,arrays, records (e.g., database records), objects, and implicit storagemechanisms. Instructions may form parts (e.g., subroutines or other codesections) of a single program, may form multiple separate programs, maybe distributed across multiple memories and processors, and may beimplemented in many different ways.

In some examples, each unit, subunit, and/or module of the system mayinclude a logical component. Each logical component may be hardware or acombination of hardware and software. For example, each logicalcomponent may include an application specific integrated circuit (ASIC),a Field Programmable Gate Array (FPGA), a digital logic circuit, ananalog circuit, a combination of discrete circuits, gates, or any othertype of hardware or combination thereof. Alternatively or in addition,each logical component may include memory hardware, such as a portion ofthe memory, for example, that comprises instructions executable with theprocessor or other processors to implement one or more of the featuresof the logical components. When any one of the logical componentsincludes the portion of the memory that comprises instructionsexecutable with the processor, the logical component may or may notinclude the processor. In some examples, each logical components mayjust be the portion of the memory or other physical memory thatcomprises instructions executable with the processor or other processorto implement the features of the corresponding logical component withoutthe logical component including any other hardware. Because each logicalcomponent includes at least some hardware even when the includedhardware comprises software, each logical component may beinterchangeably referred to as a hardware logical component.

A second action may be said to be “in response to” a first actionindependent of whether the second action results directly or indirectlyfrom the first action. The second action may occur at a substantiallylater time than the first action and still be in response to the firstaction. Similarly, the second action may be said to be in response tothe first action even if intervening actions take place between thefirst action and the second action, and even if one or more of theintervening actions directly cause the second action to be performed.For example, a second action may be in response to a first action if thefirst action sets a flag and a third action later initiates the secondaction whenever the flag is set.

Each component may include additional, different, or fewer components.For example, the gas turbine engine 100 may include additionalcomponents such as intercoolers. The dual wall turbine blade 112 mayinclude components not shown, such as a platform and/or shank.Additionally, the system 300 may be implemented with additional,different, or fewer components. The logic illustrated in the flowdiagrams may include additional, different, or fewer operations thanillustrated. The operations illustrated may be performed in an orderdifferent than illustrated.

In addition to the parameters 342 previously discussed and the examplevalues in above Table 1, the operational parameters 342 may includeadditional settings. In some examples, these parameters 342 may vary orbe set to a preferable range. For example, shown in table 2 below, twoparameters 342 may be critical parameters. One critical parameter isthat the percentage of bonding current (indicated, for one example, asweld current in the tables) must be in excess of 50%. Bonding currentmay, for example, be related to electrical current 346. The secondcritical parameter is that the time of bonding must be a fairly shorttime period, for example, 30 to 60 seconds, in order to prevent meltingand expulsion that may deform the coversheet 220 and/or surroundingpedestals 212 not targeted for bonding. Bonding time may, for example,refer to the amount of time the electrical current 346 flows across theconductive electrical path 314 between the cover sheet probe 310 and theinner pedestal probe 320.

TABLE 2 Initial Trials to Oultine Approximate Parameters Electrode Size:Generously Radiused Electrodes with 0.225″ Flat Sheet: Un-BondedNi-Flashed Lamilloy Sheet Components Parameters Pressure Weld CurrentCurrent Squeeze Load Air t- Start t- % t- Setup Read Weld Tap Time (lb)(psi) Preheat Preheat UpSlope Upslope Current Weld (A) (A) VisualInspection 1 2 30 400 31 30% 90 40% 30 50 90 Melt and Expulsion 2 2 30400 31 30% 90 40% 30 50 60 Borderline Melt 3 2 30 400 31 30% 90 40% 3050 30 OK- Bond 4 2 60 400 31 20% 90 30% 60 40 30 No-Bond 5 2 60 400 3130% 90 30% 60 40 30 No-Bond 6 2 60 400 31 30% 90 30% 60 45 30 LightlyBonded 7 2 60 400 31 30% 90 30% 60 50 30 Good Bond The data aboveindicates that greater than 50% weld current for short times are neededto produce a good bond. All welds were pulled apart for visualexamination Amperage range and readings were not recorded

In another example, additional trials were conducted to provide a moredetailed investigation of the effects of the percentage of bonding heat(indicated, for one example, as weld heat in the tables), bonding time,and up-slope parameters, for example start up-slope and/or up-slopetime. The example parameters for the trials are provided below in Table3, below, for the evaluation of heat (for example preheat, preheat time,and/or weld heat as shown in the table), bonding time, up-slope time,and preheat time.

TABLE 3 Using Standard AC Resistance Spot Welder and Copper ElectrodesElectrode Size: 0.375″/0.625″ Flat, Materials to be bonded: HA230 0.026″with Lamilloy design comfigulations of cooling holes and pedestalsResistance Bonding Parameters Pressure Weld Nugget Test Squeeze Load AirPreheat Start Time Heat Weld Size Metallurgraphic Weld Date Time (N)(kPa) Preheat Time UpSlope Upslope (%) Time (mm) Evaluations  1 Apr. 18,2001 60 1779.29 213.7375 30% 90 30% 60 50 30 4.445 Good bond, but formednugget: 0.04″ × 0.02″  2 Apr. 18, 2001 60 1779.29 213.7375 30% 90 30% 6050 30 4.064 Good bond, no nugget  3 Apr. 18, 2001 60 1779.29 213.737530% 90 30% 90 50 30 3.81 Good bond, no nugget  4 Apr. 18, 2001 601779.29 213.7375 30% 90 30% 90 45 90 0 No bond  5 Apr. 18, 2001 601779.29 213.7375 30% 90 30% 90 47 90 0 Weak bond  6 Apr. 18, 2001 601779.29 213.7375 30% 60 30% 60 55 30 4.572 Good bond, no nugget  7 Apr.18, 2001 60 1779.29 213.7375 30% 60 30% 60 60 30 4.064 Good bond, butformed nugget: 0.02″ × 0.01″  8 May 1, 2001 60 1779.29 213.7375 30% 6030% 60 65 30 4.318 Nugget: 0.1″ × 0.005″  9 May 1, 2001 60 1779.29213.7375 30% 60 30% 60 70 30 4.318 Nugget, a little metal in channelseen in micro 10 May 1, 2001 60 1779.29 213.7375 30% 60 30% 60 75 304.826 Melt metal flowed in hot side holes and channels 11 May 1, 2001 601779.29 213.7375 30% 60 30% 60 80 30 5.334 Melt metal flowed in hot sideholes and channels 12 May 1, 2001 60 1779.29 213.7375 30% 60 30% 60 8530 5.842 Melt metal flowed in hot side holes and channels 13 May 1, 200160 1779.29 213.7375 30% 60 30% 60 90 30 6.35 Melt metal flowed in hotside holes and channels

The results in the Table 3 above indicate that bonding heat percentageand bonding time have much larger effects on the integrity of the bondthan up-slope time or preheat time. The data above tends to indicatethat bonding heat percentage should preferably be held in the range of50% to 70% in order to provide a good bond between surfaces with littleor no melting. Bonding heat percentage may be related to electricalcurrent 346, electrical voltage 348, and/or the resistance of thematerials being bonded. The data also indicates that bonding time shouldpreferably be held to relatively low values, for example, below 90cycles, in order to prevent melting. When the bonding time data fromTable 2 is combined with that of Table 3, it indicates that bonding timeshould preferably be held to less than 60 cycles. The data from table 2indicates that, in one example, melting began at approximately 60cycles. Therefore it would tend to suggest that bonding time shouldpreferably be held between 30 and 50 cycles.

In another example, additional samples were manufactured to evaluate therange of acceptable bonding heat in further detail via metallography andshear testing. The parameters 342 used to generate these samples andassociated data are provided in Table 4 below for investigation ofbonding heat percentage and associated shear test results.

TABLE 4 Using Standard AC Resistance Spot Welder and Copper ElectrodesElectrode Size: 0.375″/0.625″ Flat: Materials to be bonded: Ni-Plateddiffusion bonding heat treated HA 230 with Lamilloy cooling holes andpedestals Resistance Bonding Parameters Pressure WeldHeat Nugget TestSqueeze Load Air Preheat Preheat Start Upslope % Weld SizeMetallurgraphic Weld Date Time (N) (kPa) % Time UpSlope Time CurrentTime (mm) Evaluations 14 May 9, 2001 60 1779.29 213.737 30% 60 30% 60 5030 2.794 good bond, no nugget 15 May 9, 2001 60 1779.29 213.737 30% 6030% 60 55 30 3.084 good bond, no nugget 16 May 9, 2001 60 1779.29213.737 30% 60 30% 60 60 30 3.302 good bond, no nugget 17 May 9, 2001 601779.29 213.737 30% 60 30% 60 65 30 3.81 good bond, no nugget 18 May 9,2001 60 1779.29 213.737 30% 60 30% 60 70 30 4.064 good bond, no nuggetArea RT Ultimate Tensile The following are Tensile Shear Test Specimens(mm2) Strength(UTS)/Load(Lb) 14-1T May 9, 2001 60 1779.29 213.737 30% 6030% 60 50 30 5.677408 35.23 Ksi/310 Lb 14-2T May 9, 2001 60 1779.29213.737 30% 60 30% 60 50 30 4.6387 33.33 Ksi/250 Lb 16-1T May 9, 2001 601779.29 213.737 30% 60 30% 60 60 30 7.354624 31.58 Ksi/360 Lb 16-2T May9, 2001 60 1779.29 213.737 30% 60 30% 60 60 30 6.967728 35.65 Ksi/385 Lb18-1T May 9, 2001 60 1779.29 213.737 30% 60 30% 60 70 30 7.74192 37.92Ksi/455 Lb, Expulsion 18-2T May 9, 2001 60 1779.29 213.737 30% 60 30% 6070 30 9.225788 28.67 Ksi/410 Lb, Expulsion

The results shown in Table 4 above indicate that, in one example, 70%bonding heat produces borderline results with possible melting andexpulsion. There is some variability at 70% bonding heat, as shown bythe metallography results versus the shear test results. The parameters342 that may have contributed to this variability include the appliedload, the relative degree of mating of the faces to be bonded, forexample, the surface 250 of the pedestals 212 and the inner surface 224of the cover sheet 220, as well as the amount of Ni flashing present onthe faces to be bonded. The effects of these items will be discussedlater in the report.

In another example, additional experiments were conducted investigatingvery short bond times with the aim of producing successful diffusionbonds with minimal exposure to oxidation of the bond faces. Theparameters 342 used for these trials and the results are shown in Table5 below. The data indicates that bonding becomes very sensitive withcycles that are on the order of 1/60^(th) of a second. Extremely shorttimes appear to lack robustness and may be even more sensitive whenactual manufacturing variability (pedestal size, surface condition,etc.) is introduced. This indicates short cycle times of 1/60^(th) of asecond or shorter would not be a valid approach.

TABLE 5 Investigation of Very Short Bonding Times Electrode Size:0.225″/0.625″ Flat Copper Electrodes Materials: Ni-plated and simulatedbonding heat treated HA230 0.026″ with Lamilloy holes and pedestalsParameters Pressure Pre- WeldHeat Current Current Squeeze Load Air Pre-heat Start t- % Weld Setup Read Metallurgraphic Weld Date Time (N) (kPa)heat Time UpSlope Upslope Current Time (A) (A) Evaluations 22 May 9,2001 60 1779.29 213.737 30% 60 30% 60 65 1 .5-4.2 4110 Good bond, nonugget 23 May 9, 2001 60 1779.29 213.737 30% 60 30% 60 75 2 .5-3.5 3190Weak bond, no nugget Electrode Size: 0.150″/0.160″ Square Flat(Cu-—Al3O2 and Cu—Zr), Ni-Plated diffusion bonding heat treated HA 230sheet (0.026″) with Lamilloy holes and pedestals Parameters PressureSqueeze Load Air Preheat Start Weld Date Electrode Tap Time (N) (kPa)Preheat Time UpSlope 24 Aug. 2, 2001 Cu—Zr 1 60 689.644 213.737 30% 6030% 25 Aug. 2, 2001 Cu—Zr 1 60 689.644 213.737 30% 60 30% 26 Aug. 2,2001 Cu—Zr 1 60 689.644 213.737 30% 60 30% 27 Aug. 2, 2001 Cu—Zr 1 60689.644 213.737 30% 60 30% 28 Aug. 2, 2001 Cu—Zr 1 60 689.644 213.73730% 60 30% Electrode Size: 0.160/0.180″ Square Flat (Cu-—Al3O2 andCu—Zr), Ni-Plated diffusion bonding heat treated HA 230 sheet 0.026″)with Lamilloy holes and pedestals Parameters WeldHeat Current CurrentNugget t- % Weld Setup Read Size Metallurgraphic Weld Upslope CurrentTime (A) (A) (mm2) Evaluations 24 60 65 1 .5-3.5 ? Weak bond, no nugget25 60 65 2 .5-3.0 2770 Weak bond, no nugget 26 60 70 2 .5-3.2 3060 Goodbond, no nugget 27 60 75 2 .5-3.5 3480 Good bond, no nugget 28 60 80 2.5-4.0 3820 Good bond, nugget

In another example, additional testing was conducted to evaluate theroom temperature shear strength of bonds produced in the preferablerange of 50% to 70% bonding heat. The parameters 342 evaluated and therespective test results are shown in Table 6 below. In one example, theresults indicate that 70% bonding heat produces a slightly larger bondarea (using round bonding probes, for example probe 410 shown in FIG. 5) and also a slightly higher ultimate shear strength than a lowerpercentage of bonding heat, for example 50-60%. The bond area may referto, for example, the nugget size indicated in the tables.

TABLE 6 Room Temperature Shear Strength of 60% and 70% Bonding HeatUsing Standard AC Resistance Spot Welder and Copper Electrodes ElectrodeMachined to 0.225″ diamter round at the tips (flat): Materials to bebonded: Ni-Plated diffusion bonding heat treated HA 230 with Lamilloycooling holes and pedestals Parameters Pressure WeldHeat Test SqueezeLoad Air Preheat Start Upslope % Weld Weld Date Time (N) (kPa) PreheatTime UpSlope Time Current Time Tensile Shear Tests at Room Temperature14-3 May 29, 2001 60 1779.29 213.737 30% 60 30% 60 50 30 16-3 May 29,2001 60 1779.29 213.737 30% 60 30% 60 60 30 16-3T May 29, 2001 601779.29 213.737 30% 60 30% 60 60 30 16-4T May 29, 2001 60 1779.29213.737 30% 60 30% 60 60 30 16-5T May 29, 2001 60 1779.29 213.737 30% 6030% 60 60 30 16-6T May 29, 2001 60 1779.29 213.737 30% 60 30% 60 60 3018-3 May 29, 2001 60 1779.29 213.737 30% 60 30% 60 70 30 18-3T May 29,2001 60 1779.29 213.737 30% 60 30% 60 70 30 18-4T May 29, 2001 601779.29 213.737 30% 60 30% 60 70 30 18-5T May 29, 2001 60 1779.29213.737 30% 60 30% 60 70 30 18-6T May 29, 2001 60 1779.29 213.737 30% 6030% 60 70 30 Parameters Current Nugget Room Temp Ave. Test Squeeze LoadRead Size Load Load Strength Strength Weld Date Time (N) (A) (mm2) (Lb)(N) (MPa) (MPa) Tensile Shear Tests at Room Temperature 14-3 May 29,2001 60 1779.29 1700 16-3 May 29, 2001 60 1779.29 2350 16-3T May 29,2001 60 1779.29 2350 8.2322416 330 1467.91 175.31 16-4T May 29, 2001 601779.29 2350 8.2322416 325 1445.67 175.61 16-5T May 29, 2001 60 1779.292350 6.7225672 260 1156.54 172.04 16-6T May 29, 2001 60 1779.29 23506.77418 235 1045.33 154.31 170.07 18-3 May 29, 2001 60 1779.29 304018-3T May 29, 2001 60 1779.29 3040 18-4T May 29, 2001 60 1779.29 30409.99998 450 2001.7 200.17 18-5T May 29, 2001 60 1779.29 3040 10.64514465 2068.42 194.31 18-6T May 29, 2001 60 1779.29 3040 9.225788 3251445.67 156.70 183.73

The data shown in Table 6 is very good considering that commercialliterature quotes a yield strength on base metal of HA230 as in the 35ksi to 40 ksi range. The data shown in Table 6 represents actualresistance bonding of the Ni-flashed surface without any meltingoccurring.

When considering the relatively brief bond cycle utilized and the factthat no melting occurs, questions arose concerning the elevatedtemperature strength of the bonds. Therefore, in another example,additional specimens for shear testing were manufactured for 60%, 70%,and 80% bonding heat. In one example, these specimens were designatedfor 1144.261 K shear testing with the exception of several 80% bondingheat specimens which would be utilized for generating room temperatureshear data for comparison to the data provided in Table 6. Theparameters 342 utilized and associated results are provided in Table 7below.

TABLE 7 Effects of % Bonding Heat on Elevated Temperature Shear StressUsing Standard AC Resistance Spot Welder and Copper Electrodes ElectrodeMachined to 0.225″ diamter round at the tips (flat); Materials to bebonded: Ni-Plated diffusion bonding heat treated HA 230 with Lamilloycooling holes and pedestals Resistance Bonding Parameters WeldHeatCurrent Nugget Test Squeeze Preheat Start Upslope % Weld Read Size LoadWeld Date Time Preheat Time UpSlope Time Current Time (A) (mm2) (N)Tensile Shear Tests at Room Temperature 16-7T Jun. 22, 2001 60 30% 6030% 60 60 30 2370 7.1613 177.929 16-8T Jun. 22, 2001 60 30% 60 30% 60 6030 2350 6.0645 155.688 16-9T Jun. 22, 2001 60 30% 60 30% 60 60 30 23706.9032 155.688 16-10T Jun. 22, 2001 60 30% 60 30% 60 60 30 2350 6.9032142.343 16N1a Jun. 22, 2001 60 30% 60 30% 60 60 30 2350 16N1b Jun. 22,2001 60 30% 60 30% 60 60 30 3880 18-7T Jun. 22, 2001 60 30% 60 30% 60 7030 3040 8.1935 329.168 18-8T Jun. 22, 2001 60 30% 60 30% 60 70 30 30407.6774 456.167 18-9T Jun. 22, 2001 60 30% 60 30% 60 70 30 3040 8.5161502.649 19 Jun. 22, 2001 60 30% 60 30% 60 75 30 3480 20 Jun. 22, 2001 6030% 60 30% 60 80 30 3880 20-1T Jun. 22, 2001 60 30% 60 30% 60 80 30 388012.0000 2313.08 20-2T Jun. 22, 2001 60 30% 60 30% 60 80 30 3880 11.41931979.46 20-3T Jun. 22, 2001 60 30% 60 30% 60 80 30 3880 12.7097 1934.9620-4T Jun. 22, 2001 60 30% 60 30% 60 80 30 3880 10.9677 355.858 20-5TJun. 22, 2001 60 30% 60 30% 60 80 30 3880 8.5806 444.822 20-6T Jun. 22,2001 60 30% 60 30% 60 80 30 3920 9.4639 462.615 Resistance BondingParameters Ave. Test Test Squeeze Strength Strength Temp Weld Date TimePreheat (MPa) (MPa) (K) Failure Expulsion Tensile Shear Tests at RoomTemperature 16-7T Jun. 22, 2001 60 30% 24.821136 1144.261 Bond No 16-8TJun. 22, 2001 60 30% 25.6485072 1144.261 Bond No 16-9T Jun. 22, 2001 6030% 22.5458652 1144.261 Bond No 16-10T Jun. 22, 2001 60 30% 20.61532423.4077102 1144.261 Bond No 16N1a Jun. 22, 2001 60 30% NDE (6 spots)16N1b Jun. 22, 2001 60 30% NDE (1 spot)  18-7T Jun. 22, 2001 60 30%40.1964508 1144.261 Bond No 18-8T Jun. 22, 2001 60 30% 59.70862161144.261 Bond No 18-9T Jun. 22, 2001 60 30% 59.02332424 52.976132211144.261 Bond No 19 Jun. 22, 2001 60 30% Micro 20 Jun. 22, 2001 60 30%Micro 20-1T Jun. 22, 2001 60 30% 193.05328 RT Bond Yes 20-2T Jun. 22,2001 60 30% 173.058476 RT Bond Yes 20-3T Jun. 22, 2001 60 30% 152.374196173.058476 RT Bond Yes 20-4T Jun. 22, 2001 60 30% 32.44592941 1144.261Bond Yes 20-5T Jun. 22, 2001 60 30% 51.84030075 1144.261 Bond Yes 20-6TJun. 22, 2001 60 30% 48.77925442 44.35516153 1144.261 Bond Yes

The data indicates that a bonding heat percentage of 70% produces asignificant increase in elevated temperature shear strength as comparedto a bonding heat percentage of 60%. The data also indicates that 80%bonding heat produces shear properties similar to that of the bondsproduced in the preferable range of 50% to 70%, but also producesunacceptable melting and expulsion into the flow channels 216. Ingeneral this data indicates that the repair process should preferableuse 70% bonding heat in order to produce the best possible bondproperties without melting or expulsion.

An additional question arose as to the basic inspectability of thebonds, for example, for NDT and/or NDE repair purposes. In one example,un-bonded component sheets of lamilloy were bonded in a number ofdifferent locations utilizing different parameters 342. The bonded sheetwas then NDE inspected, for example, by the bonding system 300. Theparameters 342 utilized to bond the various areas, for example thesurface area 250 of the pedestal 212 and the inner surface 224 of thecover sheet 220, are provided in Table 8 below. In one example, theparameters 16N, 17N, 18N, 19N, and 20N were utilized to bond the coversheets 220 in a number of different locations. These parameterscorrespond to 60%, 70%, 75%, and 80% bonding heat. All bonds weredetectable during inspection, this demonstrated basic inspectability.More detailed discussion of NDE inspectability and the detectability ofmelting or wicked channels will be discussed later in this report.

TABLE 8 Parameters and Arrangement on Cover Sheet for DeterminingFeasibility of NDE Inspection Electrode Size: 0.225″/0.625″ Flat;Ni-Plated diffusion bonding heat treated HA 230 with Lamilloy Electrodesmachined to 0.225″ diameter at the tip (flat) Parameters PressureWeldHeat Current Current Squeeze Load Air t- Start t- % t- Setup ReadWeld Tap Time (N) (kPa) Preheat Preheat UpSlope Upslope Current Weld (A)(A) Note Tensile Shear Tests at Room Temperature 16N 1 60 1779.29213.737 30% 60 30% 60 60 30 .5-2.5k 2370 NDE 18N 1 60 1779.29 213.73730% 60 30% 60 70 30 .5-3.5k 3040 NDE 19N 1 60 1779.29 213.737 30% 60 30%60 75 30 .5-3.5k 3480 NDE 20N 1 60 1779.29 213.737 30% 60 30% 60 80 30.5-4k   3880 NDE 21N 1 60 1779.29 213.737 30% 60 30% 60 80 30 .5-4.5k4220 NDE 21 1 60 1779.29 213.737 30% 60 30% 60 80 30 .5-5k   4220 Micro16N5s 1 60 1779.29 213.737 30% 60 30% 60 80 30 .5-2.5k 2370 NDEMaterials: Ni-plated and bonding heat treated HA230 0.026″ with holesand pedestals

Table 8, above, shows one example of the parameters 342 used for bondingthe cover sheet 220.

In one example, trials were then conducted with rectangular probes, forexample, probe 410 shown in FIG. 4 , scaling the applied stress and/orload down from that of the round probe, for example, probe 410 shown inFIG. 5 . The parameters 342 used for the first set of trials areprovided in Table 9 below. The results indicate that all samplesillustrated varying levels of melting. Some examples illustrated theonset of melting while others illustrated full melting.

TABLE 9 Initial Trials - Investigation Scaling The Applied Stress ToRectangular Electrodes Electrode Size: 0.125″ × 0.125″ square Allsamples were Ni Flashed Parameters Squeeze Load t- Start t- Weld % t-Weld Tap Time (lb) Preheat Preheat UpSlope Upslope Current Weld  1 1 9063 30% 90 30% 60 60 30 Signs of Melting  2 1 90 63 30% 90 30% 60 60 60Signs of Melting  3 1 90 63 30% 90 30% 60 60 45 Signs of Melting  4 1 9063 30% 90 30% 60 50 45 Melting  5 1 90 63 30% 90 30% 60 70 30 Melting  61 90 63 30% 60 30% 60 60 30 Signs of Melting  7 1 90 63 30% 30 30% 60 6030 Signs of Melting  8 1 90 63 30% 90 40% 60 60 30 Signs of Melting  9 190 63 30% 90 45% 60 60 30 Signs of Melting 10 1 90 63 30% 90 30% 90 6030 Melting 11 1 90 63 30% 90 30% 30 60 30 Melting 12 1 90 63 30% 90 30%60 60 30 Signs of Melting

In one example, the initial trials were then repeated using a higherload in order to insure full contact of the mating faces, for examplethe surface area 250 of the pedestal 212 and the inner surface 224 ofthe cover sheer 220. The results from these example trials are shown inTable 10 below. The results indicate that proper loading is critical.Loading may, for example, refer to pressing force 370. The dataindicates that when using proper loading, probes 410 of material Cu—Zr,a bonding current in the range of 60% to 70%, and a bonding time between30 and 60 cycles, preferable results will be produced. In one example,the parameters shown in Table 9 produce microstructures. Themicrostructure represents bond #4 and bond #5 from Table 10 below. Allother bonds were metallographically evaluated and demonstrated varyingdegrees of grain growth in the bonded interlayer of Ni flashing.

TABLE 10 Trials with high load utilizing Cu—Zr rectangular electrodesElectrode Size: 0.125″ × 0.125″ square All samples were Ni FlashedParameters Squeeze Load t- Start t- Weld % t- Weld Tap Time (lb) PreheatPreheat UpSlope Upslope Current Weld  1 1 90 600 30% 90 30% 60 60 30Bonded - No Signs of Significant Grain Growth in Ni Flash  2 1 90 60030% 90 30% 60 60 60 Bonded - No Signs of Significant Grain Growth in NiFlash  3 1 90 600 30% 90 30% 60 60 45 Bonded - No Signs of SignificantGrain Growth in Ni Flash  4 1 90 600 30% 90 30% 60 50 45 Bonded - NoSigns of Significant Grain Growth in Ni Flash  5 1 90 600 30% 90 30% 6070 30 Bonded - Evidence of Significant Grain Growth in Ni - Flash  6 190 600 30% 60 30% 60 60 30 Bonded - No Signs of Significant Grain Growthin Ni Flash  7 1 90 600 30% 30 30% 60 60 30 Bonded - No Signs ofSignificant Grain Growth in Ni Flash  8 1 90 600 30% 90 40% 60 60 30Bonded - No Signs of Significant Grain Growth in Ni Flash  9 1 90 60030% 90 45% 60 60 30 Bonded - No Signs of Significant Grain Growth in NiFlash 10 1 90 600 30% 90 30% 90 60 30 Bonded - No Signs of SignificantGrain Growth in Ni Flash 11 1 90 600 30% 90 30% 30 60 30 Bonded - NoSigns of Significant Grain Growth in Ni Flash 12 1 90 600 30% 90 30% 6060 30 Bonded - No Signs of Significant Grain Growth in Ni Flash

To clarify the use of and to hereby provide notice to the public, thephrases “at least one of <A>, <B>, . . . and <N>” or “at least one of<A>, <B>, . . . <N>, or combinations thereof” or “<A>, <B>, . . . and/or<N>” are defined by the Applicant in the broadest sense, superseding anyother implied definitions hereinbefore or hereinafter unless expresslyasserted by the Applicant to the contrary, to mean one or more elementsselected from the group comprising A, B, . . . and N. In other words,the phrases mean any combination of one or more of the elements A, B, .. . or N including any one element alone or the one element incombination with one or more of the other elements which may alsoinclude, in combination, additional elements not listed. Unlessotherwise indicated or the context suggests otherwise, as used herein,“a” or “an” means “at least one” or “one or more.”

While various embodiments have been described, it will be apparent tothose of ordinary skill in the art that many more embodiments andimplementations are possible. Accordingly, the embodiments describedherein are examples, not the only possible embodiments andimplementations.

The subject-matter of the disclosure may also relate, among others, tothe following aspects:

A first aspect relates to a method comprising: aligning a pedestal of acore of a three dimensional (3D) contoured dual wall structure to abutan inner surface of a cover sheet of the dual wall structure; abutting a3D contoured surface of a tip of a cover sheet probe against acorresponding 3D contoured outer surface of the cover sheet opposite thepedestal abutting the inner surface of the cover sheet; coupling aninner pedestal probe to the dual wall structure to create a conductiveelectrical path from the cover sheet probe through at least part of thedual wall structure; applying a predetermined localized pressing forceto the corresponding 3D contoured outer surface of the cover sheet withthe cover sheet probe; heating a junction between the inner surface ofthe cover sheet abutting the pedestal and the pedestal by controlling aflow of electric power from the cover sheet probe to the inner pedestalprobe; creating a heated area in the junction; and fixedly coupling thecoversheet and the pedestal with the heated area.

A second aspect related to the method of aspect 1, wherein fixedlycoupling the coversheet and the pedestal with the heated area comprisesdiffusion bonding in the heated area, resistance bonding in the heatedarea, or braze bonding in the heated area.

A third aspect relates to the method of any preceding aspect, whereinthe dual wall structure is a turbine blade or a turbine vane.

A fourth aspect relates to the method of any preceding aspect, whereinabutting the 3D contoured surface of the tip of the cover sheet probeagainst the corresponding 3D contoured outer surface of the cover sheetcomprises the 3D contoured surface of the tip of the cover sheet probefollowing the corresponding 3D contoured outer surface of the coversheet.

A fifth aspect relates to the method of any preceding aspect, whereinaligning the pedestal of the core with the cover sheet comprisesaligning a 3D contoured surface of the pedestal with a corresponding 3Dcontoured surface of the inner surface of the cover sheet.

A sixth aspect relates to the method of any preceding aspect, whereinthe 3D contoured surface of the inner surface of the cover sheet and the3D contoured outer surface of the cover sheet are oppositely contoured3D surfaces.

A seventh aspect relates to the method of any preceding aspect, whereincoupling the inner pedestal probe to the dual wall structure comprisespositioning the inner pedestal probe in the core to include the pedestalas part of the conductive electrical path between the cover sheet probeand the inner pedestal probe, and wherein aligning the pedestal of thecore with the cover sheet comprises applying a temporary shieldingmaterial between the pedestal and another pedestal adjacent thepedestal.

An eight aspect relates to the method of any preceding aspect, whereinheating the junction between the inner surface of the cover sheetabutting the pedestal and the pedestal by controlling the flow ofelectric power comprises heating the junction between the inner surfaceof the cover sheet and the pedestal to a localized maximum junctiontemperature of all junctions in the conductive electrical path betweenthe cover sheet probe and the inner pedestal probe.

A ninth aspect relates to the method of any preceding aspect, whereinthe pedestal is a plurality of pedestals, and the tip of the cover sheetprobe comprises a corresponding plurality of tips, and wherein abuttingthe 3D contoured surface of the tip of the cover sheet probe against thecorresponding 3D contoured outer surface of the cover sheet comprisesaligning a pattern of the pedestals on the core with a matching patternof the corresponding 3D contoured surfaces of the tips of the coversheet probe such that each of the pedestals is aligned with one of thecorresponding tips to create respective multiple maximum temperaturejunctions between the inner surface of the cover sheet and multiplerespective pedestals.

A tenth aspect relates to the method of any preceding aspect, whereinthe pedestal is a plurality of pedestals, and the cover sheet probecomprises a plurality of cover sheet probes each with a correspondingtip, and wherein abutting the tip of the cover sheet probe against theouter surface of the cover sheet comprises aligning a pattern of thepedestals on the core with a matching pattern of the cover sheet probessuch that each of the pedestals is aligned with one of the correspondingtips to create respective multiple maximum temperature junctions betweenthe cover sheet and multiple respective pedestals.

An eleventh aspect relates to the method of any preceding aspect,wherein aligning the pedestal of the core of the dual wall structure toabut the inner surface of the cover sheet of the dual wall structurecomprises the initial step of applying a braze or diffusion agent to thepedestal, wherein the braze or diffusion agent is in the form of apowder, foil, or coatings/ion implantation.

A twelfth aspect related to the method of any preceding aspect, whereincoupling the inner pedestal probe to the dual wall structure comprisesinserting the inner pedestal probe into a cooling channel inside of thecore of the dual wall component, and coupling the inner pedestal probeto an interior wall of the cooling channel to direct the conductiveelectrical path through the pedestal.

A thirteenth aspect relates to a system comprising: a resistance welder;a cover sheet probe electrically coupled with the resistance welder, thecover sheet probe comprising a tip having a three dimensional (3D)contoured contacting area that follows a 3D contoured outer surface of acover sheet of a core included in a dual wall structure; an innerpedestal probe electrically coupled with the resistance welder, theinner pedestal probe to electrically couple with the dual wallstructure; and the resistance welder including a controller to control asupply of electric power to the cover sheet probe and control a pressingforce of the tip of the cover sheet probe against the outer surface ofthe cover sheet, wherein the tip includes the 3D contoured contactingarea to abut the 3D contoured outer surface of the cover sheet oppositean inner surface of the cover sheet, the inner surface abutting apedestal included in the core, and the 3D contoured contacting areaequal to or greater than a surface area of the pedestal contacting theinner surface of the cover sheet.

A fourteenth aspect relates to the system of aspect 13, wherein the 3Dcontoured contacting area of the tip of the cover sheet probecorresponds to only a portion of the 3D contoured surface of the coversheet.

A fifteenth aspect relates to the system of any preceding aspect,wherein the 3D contoured contacting area of the tip creates a conductiveelectrical path of lower resistance between the 3D contacting area ofthe tip and the 3D contoured outer surface of the cover sheet ascompared to a junction formed between the inner surface of the coversheet and the pedestal.

A sixteenth aspect relates to the system of any preceding aspect,wherein the junction formed between the inner surface of the cover sheetand the pedestal is a localized maximum temperature junction along aconductive electrical path having a plurality of other junctions betweenthe cover sheet probe and the inner pedestal probe.

A seventeenth aspect relates to the system of any preceding aspect,wherein the pedestal is a plurality of pedestals, and the tip of thecover sheet probe comprises a corresponding plurality of tips, wherein apattern of the tips of the cover sheet probe match a pattern of thepedestals such that each of the pedestals is aligned with one of thecorresponding tips.

An eighteenth aspect relates to the system of any preceding aspect,wherein the pedestal is a plurality of pedestals, and the cover sheetprobe comprises a plurality of cover sheet probes and a correspondingplurality of respective tips, wherein a pattern of the respective tipsof the cover sheet probes match a pattern of the pedestals such thateach of the pedestals is aligned with one of the correspondingrespective tips.

A nineteenth aspect relates to the system of any preceding aspect,wherein a 3D contoured outer surface of the pedestal follows a 3Dcontoured surface of the inner surface of the cover sheet, and the 3Dcontoured surface of the inner surface of the cover sheet is contouredopposite to the 3D contoured outer surface of the cover sheet.

A twentieth aspect relates to the system of any preceding aspect,wherein the inner pedestal probe is dimensioned for insertion into acooling channel inside of the core of the dual wall component and isconfigured to couple with an interior wall of the cooling channel toform a conductive electrical path from the cover sheet probe through atleast part of the pedestal to the inner pedestal probe.

In addition to the features mentioned in each of the independent aspectsenumerated above, some examples may show, alone or in combination, theoptional features mentioned in the dependent aspects and/or as disclosedin the description above and shown in the figures.

What is claimed is:
 1. A system comprising: a dual wall structure, thedual wall structure including a core and a cover sheet, the cover sheethaving a 3D contoured outer surface; a resistance welder; a cover sheetprobe electrically coupled with the resistance welder, the cover sheetprobe comprising a tip having a three dimensional (3D) contouredcontacting area that follows the 3D contoured outer surface of the coversheet of the dual wall structure; an inner pedestal probe electricallycoupled with the resistance welder, the inner pedestal probe toelectrically couple with the dual wall structure; and the resistancewelder including a controller to control a supply of electric power tothe cover sheet probe and control a pressing force of the tip of thecover sheet probe against the outer surface of the cover sheet, whereinthe tip includes the 3D contoured contacting area to abut the 3Dcontoured outer surface of the cover sheet opposite an inner surface ofthe cover sheet, the inner surface abutting a pedestal included in thecore, and the 3D contoured contacting area equal to or greater than asurface area of the pedestal contacting the inner surface of the coversheet.
 2. The system of claim 1, wherein the 3D contoured contactingarea of the tip of the cover sheet probe corresponds to only a portionof the 3D contoured surface of the cover sheet.
 3. The system of claim2, wherein the 3D contoured contacting area of the tip creates aconductive electrical path of lower resistance between the 3D contactingarea of the tip and the 3D contoured outer surface of the cover sheet ascompared to a junction formed between the inner surface of the coversheet and the pedestal.
 4. The system of claim 1, wherein a junctionformed between the inner surface of the cover sheet and the pedestal isa localized maximum temperature junction along a conductive electricalpath having a plurality of other junctions between the cover sheet probeand the inner pedestal probe.
 5. The system of claim 1, wherein thepedestal is a plurality of pedestals, and the tip of the cover sheetprobe comprises a corresponding plurality of tips, wherein a pattern ofthe tips of the cover sheet probe match a pattern of the pedestals suchthat each of the pedestals is aligned with one of the correspondingtips.
 6. The system of claim 1, wherein the pedestal is a plurality ofpedestals, and the cover sheet probe comprises a plurality of coversheet probes and a corresponding plurality of respective tips, wherein apattern of the respective tips of the cover sheet probes match a patternof the pedestals such that each of the pedestals is aligned with one ofthe corresponding respective tips.
 7. The system of claim 1, wherein a3D contoured outer surface of the pedestal follows a 3D contouredsurface of the inner surface of the cover sheet, and the 3D contouredsurface of the inner surface of the cover sheet is contoured opposite tothe 3D contoured outer surface of the cover sheet.
 8. The system ofclaim 1, wherein the inner pedestal probe is dimensioned for insertioninto a cooling channel inside of the core and is configured to couplewith an interior wall of the cooling channel to form a conductiveelectrical path from the cover sheet probe through at least part of thepedestal to the inner pedestal probe.
 9. The system of claim 1, whereinthe cover sheet, core, and pedestal are part of a turbine blade or aturbine vane.
 10. The system of claim 1, wherein a 3D contoured surfaceof the inner surface of the cover sheet and the 3D contoured outersurface of the cover sheet are oppositely contoured 3D surfaces.
 11. Thesystem of claim 1, a 3D contoured surface of the pedestal aligns andcorresponds with a 3D contoured surface of the inner surface of thecover sheet.
 12. The system of claim 1, wherein the resistance welder isconfigured to resistance bond, diffusion bond, or braze bond.
 13. Thesystem of claim 1, wherein a braze or a diffusion agent is disposed onthe pedestal between the pedestal and the coversheet.
 14. A systemcomprising: a resistance welder; a cover sheet probe electricallycoupled with the resistance welder, the cover sheet probe comprising atip having a three dimensional (3D) contoured contacting area thatfollows a 3D contoured outer surface of a cover sheet of a dual wallstructure; an inner pedestal probe electrically coupled with theresistance welder, the inner pedestal probe to electrically couple withthe dual wall structure; and the resistance welder including acontroller to control a supply of electric power to the cover sheetprobe and control a pressing force of the tip of the cover sheet probeagainst the outer surface of the cover sheet, wherein the tip includesthe 3D contoured contacting area to abut the 3D contoured outer surfaceof the cover sheet opposite an inner surface of the cover sheet, theinner surface abutting a pedestal included in the core, and the 3Dcontoured contacting area equal to or greater than a surface area of thepedestal contacting the inner surface of the cover sheet, wherein thepedestal is a plurality of pedestals, and the tip of the cover sheetprobe comprises a corresponding plurality of tips, and wherein the 3Dcontoured surface of the tip of the cover sheet probe is configured toabut the corresponding 3D contoured outer surface of the cover sheet,wherein a pattern of the pedestals included in the core match a patternof the 3D contoured contacting surfaces of the corresponding pluralityof tips of the cover sheet probe tip such that each of the pedestalsaligns with one of the corresponding plurality of tips to create arespective maximum temperature junction between the cover sheet and arespective pedestal.
 15. A system comprising: a resistance welder; acover sheet probe electrically coupled with the resistance welder, thecover sheet probe comprising a tip having a three dimensional (3D)contoured contacting area that follows a 3D contoured outer surface of acover sheet of a dual wall structure; an inner pedestal probeelectrically coupled with the resistance welder, the inner pedestalprobe to electrically couple with the dual wall structure; and theresistance welder including a controller to control a supply of electricpower to the cover sheet probe and control a pressing force of the tipof the cover sheet probe against the outer surface of the cover sheet,wherein the tip includes the 3D contoured contacting area to abut the 3Dcontoured outer surface of the cover sheet opposite an inner surface ofthe cover sheet, the inner surface abutting a pedestal included in thecore, and the 3D contoured contacting area equal to or greater than asurface area of the pedestal contacting the inner surface of the coversheet, wherein the pedestal is a plurality of pedestals, and the coversheet probe comprises a plurality of cover sheet probes each with acorresponding tip, and wherein the tip of the cover sheet probe isconfigured to abut against the outer surface of the cover sheet, whereina pattern of the pedestals included in the core match a pattern of the3D contoured contacting surfaces of the corresponding tips of thecoversheet probe such that each of the pedestals aligns with one of thecorresponding tips to create a respective maximum temperature junctionbetween the cover sheet and a respective pedestal.